Added gcd function

Author: IPRIT

src/lib/math/greatest-common-divisor/greatest-common-divisor.spec.ts

@@ -0,0 +1,39 @@
+// tslint:disable:no-expression-statement
+import test from 'ava';
+import { greatestCommonDivisor } from './greatest-common-divisor';
+
+test('finds GCD of positive numbers', t => {
+  const tests = [
+    [[2, 5], 1],
+    [[1000026, 2330], 2],
+    [[100000004, 244127], 13],
+    [[1000000001, 513], 19]
+  ];
+  for (const vtest of tests) {
+    const [v, a] = vtest;
+    // @ts-ignore
+    t.is(greatestCommonDivisor(...v), a);
+  }
+});
+
+test('finds GCD of negative numbers', t => {
+  const tests = [
+    [[-2, -5], 1],
+    [[-1000026, -2330], 2],
+    [[-100000004, -244127], 13],
+    [[-1000000001, -513], 19]
+  ];
+  for (const vtest of tests) {
+    const [v, a] = vtest;
+    // @ts-ignore
+    t.is(greatestCommonDivisor(...v), a);
+  }
+});
+
+test('finds GCD of 1 and 1', t => {
+  t.is(greatestCommonDivisor(1, 1), 1);
+});
+
+test('works GCD with zero values', t => {
+  t.is(greatestCommonDivisor(0, 0), 1);
+});

src/lib/math/greatest-common-divisor/greatest-common-divisor.ts

@@ -0,0 +1,35 @@
+/**
+ * Returns greatest common divider from number using iterative Euclid's algorithm
+ * @link https://en.wikipedia.org/wiki/Euclidean_algorithm
+ *
+ * Iterative algorithm much faster (in average ~1.335) than recursive
+ *
+ * @param {number} a
+ * @param {number} b
+ * @returns {number}
+ */
+export function greatestCommonDivisor(a: number, b: number): number {
+  a = Math.abs(a);
+  b = Math.abs(b);
+
+  if (a === b && a === 0) {
+    return 1;
+  }
+
+  if (b > a) {
+    const temp = a;
+    a = b;
+    b = temp;
+  }
+
+  while (true) {
+    a %= b;
+    if (a === 0) {
+      return b;
+    }
+    b %= a;
+    if (b === 0) {
+      return a;
+    }
+  }
+}

src/lib/math/index.ts

@@ -1,3 +1,4 @@
 export * from './is-power-of-two/is-power-of-two';
 export * from './nearest-highest-power-of-two/nearest-highest-power-of-two';
 export * from './nearest-highest-power-of-two-result/nearest-highest-power-of-two-result';
+export * from './greatest-common-divisor/greatest-common-divisor';

yarn.lock

@@ -2053,7 +2053,7 @@ inflight@^1.0.4:
     once "^1.3.0"
     wrappy "1"
 
-inherits@2, inherits@^2.0.1, inherits@^2.0.3, inherits@~2.0.3:
+inherits@2, inherits@^2.0.3, inherits@~2.0.3:
   version "2.0.4"
   resolved "https://registry.yarnpkg.com/inherits/-/inherits-2.0.4.tgz#0fa2c64f932917c3433a0ded55363aae37416b7c"
   integrity sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==
@@ -3653,14 +3653,6 @@ set-blocking@^2.0.0:
   resolved "https://registry.yarnpkg.com/set-blocking/-/set-blocking-2.0.0.tgz#045f9782d011ae9a6803ddd382b24392b3d890f7"
   integrity sha1-BF+XgtARrppoA93TgrJDkrPYkPc=
 
-sha.js@^2.4.11:
-  version "2.4.11"
-  resolved "https://registry.yarnpkg.com/sha.js/-/sha.js-2.4.11.tgz#37a5cf0b81ecbc6943de109ba2960d1b26584ae7"
-  integrity sha512-QMEp5B7cftE7APOjk5Y6xgrbWu+WkLVQwk8JNjZ8nKRciZaByEW6MubieAiToS7+dwvrjGhH8jRXz3MVd0AYqQ==
-  dependencies:
-    inherits "^2.0.1"
-    safe-buffer "^5.0.1"
-
 shebang-command@^1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/shebang-command/-/shebang-command-1.2.0.tgz#44aac65b695b03398968c39f363fee5deafdf1ea"